Ignitron seal



p 1933- D. E. MARSHALL 30,888

IGNITRON SEAL Filed Feb. 20, 1956 L In/ef .Sfarfer' WITNESSES: INVENTORATTORNE Patented Sept. 20, 1 938 UNITED STATES PATENT OFFICE IGNITRONSEAL of Pennsylvania Application February 20, 1936, Serial No. 64,880

8 Claims.

My invention relates to electrical discharge devices and particularlytosuch devices having a conductor sealed through an insulating portion ofthe container wall.

An object of my invention is to protect the seal between an insulatingand metallic portion of an electrical discharge device from excessiveheat.

Another object of my invention is to permit the use of material withgood sealing properties although such material may not have good heatconducting properties.

Other objects of my invention will become apparent on reading thefollowing description taken in conjunction with the drawing, in whichthe figure represents a cross section through an electrical dischargedevice with certain parts in elevation.

Because my invention isespecially useful in its application toelectrical discharge devices suitable for welding systems, I haveillustrated the application of my invention to such an electrondischarge device although the invention is not to be construed as beinglimited to such a particular device or use of the device.

In electric discharge devices for welding the excessive heating of theelectrodes and their connections is quite a problem. This is due to theunusually large root mean square current necessary in this type ofservice. In one case,in the tube of 40 amperes average the tube has aroot mean square value of 250 amperes. Accordingly, it became necessaryto provide additional precautions for the heating effect of thisexcessive root mean square current.

Another problem which I have solved in my invention is that of utilizingeffectively a composition of 23% to 34% nickel, 9% to 25% cobalt,

less than 1% manganese and the remainder iron or principally iron foruse as sealing material in devices in which a large current passesthrough this material. The material or alloy just mentioned is moreparticularly described in the copending application of Howard Scott,Serial No. 376,291 for Glass metal seals, filed July 5, 1929. This alloyhas the great advantages that it can be sealed vacuum tight to glass andyet will withstand mercury vapor and can be easily machined into anydesired shape. This alloy, however, does not have as good a heatconductivity or as low an electrical resistance as copper, for example.Due to the fact that this alloy can be sealed to glass without thespecial feather edge sealing process necessary with copper, this alloyis much more desirable as a sealing metal for glass. Where a tube,however, is used in which a very high current passes through the metaland where excessive heat is created in the device, then it is advisableto take into account the lower heat conductivity and higher electricalresistance of this excellent glass sealing alloy.

My invention permits the use of this alloy as glass sealing materialwithout danger to the seal from the excessive heat due to the operationof the device or to the high current passing through the alloy.

In the preferred form of the device, the container has a cup-shapedmetal portion Iil holding the mercury pool II. An insulating portion l2of the container is sealed thereto. The metal of the electrode I Iprefer to have of an alloy of 23% to 34% nickel, 9% to 25% cobalt, lessthan 1% manganese and the remainder iron and the insulating portion l2of a boron silicate glass such as is more particularly described in thecopending application of Howard Scott above referred to. An electricalconnection 21 for this cathode arrangement can be welded or otherwiseconnected to the cup [0. Within the container is the anode l3 of iron orcarbon and the device also preferably contains the starter 14 withsuitable electrical connections thereto. This starter is preferably ofthe make-alive type having a high refractory material in contact withthe mercury pool I I. The make-alive type of starter is moreparticularly described in the copending application of Joseph Slepian,et al., Serial No. 626,866, for Electric are devices, filed July 30,1932. The preferred material for the make-alive is boron carbide.

My invention particularly concerns the conductor for the anode l3 sealedthrough the insulating portion l2. In the preferred embodiment of myinvention, I have'preferably a tubular member l5 sealed through theinsulating material l2 and supporting the anode l3 on the inner endthereof. While any well known manner of support may be used, I prefer touse an extension [8 on the inner end of the tube screwed into the anode,as disclosed in the drawing. I also prefer to havethe insulating portion[2 sealed to the cylindrical sides I! of the tube 15. This seal, asshown, can extend over quite an area of the cylindrical sides in orderto form an extensive and strong seal therewith. The tube l5 has a hollowportion l8 extending preferably below the lower edge I9 of the seal.Extending through this hollow portion It! is a conductor 20 of high heatconductivity, such as copper or silver, connected at the lowest point 2|to the metal tube, which point is closer to the anode l3 than thebeginning of the glass portion of the seal at the point Hi. Thisconductor 28 may be in the form of a solid or stranded conductor or, asshown, may comprise a second tubular member with a hollow portion 22 forcooling means, such as water, to flow therethrough to holes 23 in thelower portion thereof and out through the space I8, thus cooling thewalls of the metal tube [5 adjacent the seal on the sides ll. Suitableinlet pipe 24,'outlet pipe 25 and electrical connection 26 can beassembled with tubes I5 and 20.

It will be noted that the electrical current will pass through theelectrical conductor from the point 2| through the extension [5 of themetal alloy tube [5 to the anode [3 without coming in contact with asection of the seal in its direct path. In other words, the seal I1 isout of the direct path of current flow to the anode. The amount of alloymaterial between the anode and the inner tip 2| of the copper connection20 is very small and accordingly the increased resistance due to thehigher electrical resistance of the alloy material will be very small.

Of much greater importance is the fact that the flow of heat from thehot anode passing through the alloy metal of the extension It will reachthe tip 2| of the copper conductor before it reaches the face of theseal IT. The good heat conducting property of the copper conductor willprovide an easier path for the flow of this heat to the conduits for thecooling water. The heat will be abstracted from the extension N5 of thealloy material to the copper connection and a dangerous amount will notflow to the seal. The construction of the device will, accordingly,permit the rapid extraction of dangerous heat from the anode and willalso provide a cooling means for the seal.

Many modifications are, of course, possible in the specific form, numberand arrangement of the elements shown and described. Accordingly, theclaims are to be given the broadest interpretation of which their termsare susceptible in view of the limitations imposed by the prior art.

I claim as my invention:

1. An electrical discharge device comprising a casing having aninsulating portion, a metal tube, a seal between said insulating portionand said tube, an electrode attached to the inner end of said tube and ametal of high conductivity attached to the said tube at at least twopoints on opposite sides of said seal.

2. An electrical discharge device comprising a casing having aninsulating wall portion, an al- 10y of 23% to 34% nickel, 9% to 25%cobalt, less than 1% manganese and the remainder iron, a vacuum-tightseal between said alloy and said insulating wall portion, an electrodeinside said casing connected to said alloy and an electric and good heatconductor connected to said alloy on the exterior of said casing.

3. An electrical discharge device comprising a casing having aninsulating wall portion, a tube of 23% to 34% nickel, 9% to 25% cobalt,less than 1% manganese and the remainder iron, a vacuum-tight sealbetween the cylindrical sides of said tube and said insulating wallportion, an electrode within said casing supported by said tube, and aconductor exterior to said casing connected to the inner portion of saidtube.

4. An electrical discharge device comprising a casing having aninsulating portion, a tube of 23% to 34% nickel, 9% to 25% cobalt, lessthan 1% manganese and the remainder iron, a vacuumtight seal between thecylindrical sides of said tube and said insulating portion sealed to thecylindrical sides of said tube, an electrode within said casingsupported by said tube, and a conductor exterior to said casingconnected to the inner portion of said tube and cooling means for saidconductor and tube.

5. An electrical discharge device comprising a casing having aninsulating portion, a conductor structure, a seal between said conductorstructure and said insulating portion, said conductor structure havinginnerand outer electrical conducting paths past said seal, said innerpath being more highly conductive than said outer path in the region ofsaid seal.

6. An electrical discharge device comprising a casing having aninsulating portion, a conductor structure, a seal between said conductorstructure and said insulating portion, said conductor structurecomprising an outer material having substantially the same coefiicientof expansion as said insulating portion and an inner material having agreater electrical conductivity than said outer material, both saidmaterials being connected at least on opposite sides of said seal.

'7. An electrical discharge device comprising a casing having aninsulating portion, a conductor structure, a seal between said conductorstructure and said insulating portion, said conductor structure havingan outer electrical conducting path of nickel-cobalt-iron alloy and aninner electrical conducting path of copper in the region of said seal.

8. An electrical discharge device comprising a casing having aninsulating portion, a conductor structure, a seal between said conductorstructure and said insulating portion, said conductor structurecomprising an outer tubular portion having substantially the samecoefficient of expansion as said insulating portion and an inner hollowcore having greater electrical conductivity than said outer portion andof such diameter as to leave a space between the two, both said tubu--lar portion and hollow core being connected to each other water-tightat least on opposite sides of said seal and an inlet and outlet forfluid in said conductor structure outside said seal.

DONALD E. MARSHALL.

